The G&P will be usable for both right out of the box without needing to buy a second spring or open up the gun but the ARES has a programmable FCU for bursts and such. That aside my favorite would probably be
http://www.evike.com/products/49144/ its that ARES but longer Modular rail so you can also have a more forward and stable grip. Before buying online check with Command Post its a local shop I know use to have some and when I saw them they were offering to use their programmer (doesn't come with gun) to program the fire modes if you buy it there.
Happy airsofting